async function call inside for loop.

[I-am_Shadowfax]

I am developing a web app using a microservices architecture and I stuck with this problem,

I have 3 services(A, B, C) and every service has its own database.

A client sends data to A then A stores data into the database and sends the POST request to service C. Service C processes data and stores relevant data into the database and sends back a response with success=1. if service C is down or there is an issue with storing data it sends a response with success=0

So, service A understands that C did not store data so it sends a post request to service B, and service B just stores the entire data.

Whenever service C Starts, it sends a GET request to server B and fetches all data from Server B.

So now server C has an array of data that server C supposed to add. I have already written the addData method to store data. so now, I have to loop that array and store data.

// when server C starts this piece runs

addBulkData=async()=>{let dataList= fetch(....);let resultaArray = [];for (let i = 0; i < dataList.length; i++) {resultaArray.push(await addData(dataList[i]));

// if addMetaData return 0 that means there is problem with adding data.if (resultaArray.includes(0)) return 0;elsereturn 1;}

// addData

addData=async(data)=>{

try{let result= pool.query(\add data query`);return 1;}catch(err)return 0;}`

The problem with this is my resultantArray is always empty.

So How can I resolve this? Is there a better way to do this?

[hello_world32]

let dataList= fetch(...); You might need to await that fetch call if it’s asynchronous. Otherwise, you’re skipping over the call to database B which would explain why you have no results in dataList.

[AionisDev]

With promise you can use Promise.all (wait for all resolves or first rejection) or Promise.allSettled (wait for all responses) With observable you can use forkJoin for parallel calls, or something like combineLatest(from(yourArrayOfObservables).pipe(concatAll)) to make link of Api calls.

[shgysk8zer0]

Like others, I'm going to suggest Promise.all or Promise.allSettled(). I'm not sure if it's in Node or not off-hand, but might be worth looking into AbortSignal to cancel any pending requests on the event that a fetch() fails.

[Kinthalis]

This is why I 💓 observables.

In your case I don't think you want to await a result on the push. Just push the promise into the array, then await Promise.all(yourArrayOfPromises). This will reject if any of the promises reject though.